Autonomous Localized Permeability Material Systems and Methods for Using and Making Same

ABSTRACT

Autonomous localized permeability material systems are provided that can include: a dynamically permeable porous material; and immobilized reagents operatively associated with the porous material in sufficient proximity to trigger a localized change in material pore size upon reagent reaction. Methods for preparing these materials are also provided as well as methods for autonomously modifying localized permeability of material.

CLAIM FOR PRIORITY

This application claims priority to U.S. Provisional Patent ApplicationSer. No. 62/452,490 filed Jan. 31, 2017, entitled “Autonomous LocalizedPermeability Material Systems and Methods for Using and Making Same”,the entirety of which is incorporated by reference herein.

GOVERNMENT INTEREST

This invention was made with Government support under Contract No.HDTRAI-13-C-0003 awarded by the Defense Threat Reduction Agency (DTRA).The Government has certain rights in the invention.

TECHNICAL FIELD

The present disclosure relates generally to porous materials andautonomous control of the permeability of these materials.

BACKGROUND

Porous materials have numerous uses crossing over from the chemicaland/or biologically protective to the recreational and even industrialuses. As an example, chemical and biological protective clothingutilizes layering technology, wherein static barrier materials arestacked to mitigate contaminant breakthrough. In recent years thesematerials have been enhanced, but these enhancements do not provide thespeed, selectivity, or molecular capacity to address complex threats asthey arise in dynamic environments. In addition, the complexity ofproduction and limited lifetime of these older materials may result inunsustainable financial costs that limit the benefits of protectivetechnologies to small numbers of personnel. An additional challenge,however, is that these enhancements do not address the significantphysical burden to the user due to the poor water vapor transport, heatmanagement, and sheer bulk of the material. As a result of theseshortcomings, users typically can only operate in full protective statefor less than an hour at a time.

The present disclosure provides autonomous localized permeabilitymaterial systems that can provide superior performance to that of theexisting material systems.

SUMMARY OF THE DISCLOSURE

Autonomous localized permeability material systems are provided that caninclude: a dynamically permeable porous material; and immobilizedreagents operatively associated with the porous material in sufficientproximity to trigger a localized change in material pore size uponreagent reaction.

Autonomous localized permeability material system preparation methodsare provided that can include operatively associating immobilizedreagents with a dynamically permeable porous material.

Methods for autonomously modifying localized permeability of materialare also provided. These methods can include: providing a dynamicallypermeable porous material operatively associated with immobilizedreagents; reacting the reagents with a reactant to form a product; andexposing the product to the dynamically permeable porous material, withthe exposing of the product modulating the permeability of the material.

DRAWINGS

Embodiments of the disclosure are described below with reference to thefollowing accompanying drawings.

FIG. 1 depicts a series of material systems according to multipleembodiments of the disclosure.

FIG. 2 depicts SEM images of material systems according to embodimentsof the disclosure.

FIG. 3 depicts images and data relating to material systems preparedaccording to embodiments of the disclosure.

FIG. 4 depicts SEM images of material systems according to embodimentsof the disclosure.

FIG. 5 depicts a sequence of reactant exposure to material systems ofthe present disclosure.

FIG. 6 depicts another sequence of reactant exposure and reset accordingto an embodiment of the disclosure.

FIGS. 7A and 7B depict open and closed configurations of porous materialas well as data associated with same according to an embodiment of thedisclosure.

FIG. 8 depicts data indicating the permeability of material systems ofthe present disclosure.

FIG. 9 depicts SEM images of material systems according to embodimentsof the disclosure.

FIGS. 10A and 10B provide SEM images and material characterization dataof material systems according to embodiments of the disclosure.

FIG. 11 depicts SEM images and permeability data of material systemsaccording to embodiments of the disclosure.

FIG. 12 depicts SEM images and permeability data of material systemsaccording to embodiments of the disclosure.

FIG. 13 depicts an example material system according to an embodiment ofthe disclosure.

FIG. 14 depicts enzyme activity data of material systems according toembodiments of the disclosure.

FIGS. 15A and 15B provide enzyme activity data of stored materialsystems according to embodiments of the disclosure.

FIGS. 16-24 are representations of data acquired in accordance withembodiments of the disclosure.

DESCRIPTION

The present disclosure provides autonomous localized permeabilitymaterial systems and methods for using and making same. In accordancewith example implementations, these systems can be used as part of aprotective material which only at the point of contact with a reagent,locally switches into a closed protective state. Other exampleconfigurations include but are not limited to industrial and/orrecreational uses.

In accordance with example implementations, the material systems of thepresent disclosure can include a dynamically permeable porous material,and one or more immobilized reagents operatively associated with theporous material in sufficient proximity to trigger a localized change inmaterial pore size upon reagent reaction. The material systems can beconsidered membranes and/or membrane systems. The material systems canbe an entirety of a material or a portion of a material, such as a layerof same.

The material systems of the present disclosure can be considered anautonomous self-decontaminating selectively responsive porous materialsystem that senses and reacts with target analyte(s) in the environmentto produce triggers for material response.

The responsive porous material can include immobilized reagent(s)chemically configured to recognize and/or convert target analytes(reactants) into chemical triggers. The target analytes or reactants caninclude but not limited to the chemical warfare agents sarin, soman,sulfur mustard; pesticides parathion, paraoxon, diisopropylfluorophosphate, and biomolecules including glucose, carbon dioxide, andglutathione. These reactants can be converted into triggers to actuate amaterial response such as the modulation of porosity of the material.

Referring to FIG. 1, example implementations 10 a, 10 b, and 10 c aredepicted. While these implementations are not exhaustive, as others areenvisioned, these three provide a sound basis to support the disclosure.Porous material 12 can include, but is not limited to materials that mayhave narrow pore size distribution in the nanometer range and highseparation efficacy with the mechanical robustness of a rubber-toughenedglassy polymer matrix, for example. The porous material can includeblock copolymer porous materials characterized by meso to microporousand even nanoporous size configurations.

As one example, triblock terpolymer such aspoly(isoprene-b-styrene-b-4-vinylpyridine) (ISV) (P4VP) can serve as thebasis for the porous material.

In accordance with other implementations, ISV can be the porousmaterial. The P4VP part of the ISV can also be 3-amino or 2-aminopyridine, as shown in the tetrablock quarterpolymer. Other embodimentsof the responsive polymer include isoprene-styrene-PDMAEMA andisoprene-styrene-HEMA, both of which are triblock terpolymers.

With reference to 10 a, porous material 12 may have reagent 14integrated therein with at least some of reagent 14 being locatedsufficiently proximate a surface of porous material 12 to react with areactant upon exposure of the system to the reactant. This form ofintegration can be the modification of the porous material itself, suchas the modification of the terminal ends of block polymers used information of the porous material. For example, reagents may be includedduring the porous material forming process, such as at least partiallyinorganic materials that may remain reactive upon porous materialformation. Such materials can include metals and/or metal organicframeworks.

In accordance with example implementations, the immobilized reagent canbe stoichiometric or catalytic. The immobilized reagent can include oneor more of enzymes, metal organic frameworks, metal oxides, nucleophilicamines, and oximes. In accordance with example implementations, thereagent can generate products, such as stimulus (triggers), uponreaction with the reactant; the reaction products can include but arenot limited to acids, bases, and/or thiols. Other implementations of thedisclosure include systems with reagents that degrade reactants butgenerate by-products that have no impact on the porous material. In someof these configurations, multiple reagents can be incorporated, with atleast one reagent generating a product upon exposure to a reactant, andthe product initiating a change in the porous material.

With reference to 10 b, porous material 12 may have reagent 14 bondedand/or adsorbed thereto. The bonding may be covalent in nature and/ornon-covalent. Just one example of the reagents that may be bonded to theporous material include a hydrolase such as a phosphotriesterase enzyme,haloalkane dehalogenase enzyme or other enzymes.

With reference to 10 c, porous material 12 may have another layer bondedthereto that may include integrated and/or bonded reagents 14. Inaccordance with example implementations, one or more of theimplementations of 10 a-10 c can be supported by another layer 16. Layer16 may be woven nylon for example.

The porous material can respond to exposure to triggers including butnot limited to pH, redox potential, and group polarity. The reagentsimmobilized with the material can be selected and/or configured toproduce products that initiate such triggers (pH changes for example).

Operatively associated with the porous materials can be specifiedreagents. With reference to FIG. 1, as stated above, the reagents(catalysts in some examples) can be enzymes. These enzymes can displayhigh reactant (substrate) specificity and fast response times.

Select variants of these reagents are capable of generating largechanges in pH with reactant (substrate, for example) specificity andresponse times toward a number of chemical and biological agents ofinterest. In accordance with example configurations, coupling theselectivity and response of enzymes with stimuli responsive materials,the dynamic material system can be prepared which responds only toreactants (e.g., enzyme substrates) with high sensitivity.Phosphotriesterase (PTE, EC 3.1.8.1) can be selected for the rapiddetoxification of a wide range of reactants such as organophosphatepesticides and chemical agents. Hydrolysis of these reactants via PTEcatalysis can generate strong and weak acid products. Incorporation ofPTE into the ISV materials can effectively create a lock-and-key-typepermeability barrier to chemical diffusion.

The materials are compatible with large area fabrication and integrationwith other support and protective materials to achieve requiredproperties including material strength, moisture vapor transmissionrates (MVTR), as well as fast response times. In accordance with exampleimplementations, the material system can include the porous material onnylon-based support structures, such as casting on macroporous wovennylon support layers. The material system can have an elastic moduli ofgreater than 300 MPa.

With reference to FIG. 2, SEM structural characterization of nylonsupport (left, top: 0.1 μm top surface; middle: 0.2 μm top surface;bottom: 0.2 μm cross section), nylon-supported material system withfinger-like substructure (middle), and material system with sponge-likesubstructure (right) are shown. For material system images, top: surfacestructure, middle: neat material system cross section, bottom: crosssection of nylon supported material systems (material surface morphologyand cross section can be characterized by field emission scanningelectron microscopy (Tescan Mira₃ FESEM). Sample surfaces can be coatedwith gold palladium at a current of 40 mA for 6 seconds (Denton VacuumDesk II) prior to imaging. Average pore sizes from FESEM micrographs canbe analyzed with Mathematica. Transmission Electron Microscopy (TEM) canbe performed using a JEOL 2000 EX electron microscope operated at 200kV. Imaging can be done by amplitude and phase contrast, and images canbe acquired using a Gatan Orius SC600 high-resolution camera. Samplescan be stained for 2-30 seconds with Phosphotungstic Acid (PTA) toincrease the contrast between the P₄VP/enzyme components and the porousmaterial.

With reference to FIG. 3, the material systems can be pliable yetrobust; maintaining physical and mechanical integrity under extensiveexperimental manipulation, including permeability testing underpressures up to 30 psi. Systems were found to exhibit “open” statepermeability in excess of Lp=200 Lm⁻²hr⁻¹bar⁻¹ and the fidelity ofpH-induced permeability changes can exceed 1 db. Permeability andtransduction characteristics can be uniform across large area materialsystems.

Critical textile properties of the material systems can be evaluatedincluding moisture vapor transport rate (MVTR), intrinsic water vaporresistance and durability (FIG. 3 b, c, FIG. 4). With reference to FIG.3, textile properties of material systems were characterized. In FIG. 3a) brittle character of neat material system (left), pliable quality ofnylon supported material system (middle), and scale-up potential ofmaterial systems via large area (4″×5″) blade casting (right) aredepicted. In FIG. 3 b), moisture vapor transport rates (MVTR) based onthe British Standard BS 7209 of supported ISV systems and commercialmaterials (PTFE, PU) are depicted by way of bar graph. In FIG. 3 c),supported material system permeability profile post flexes testing(left) and tensile testing (right) are shown.

Referring next to FIG. 4, SEM micrographs of supported material systembefore and after durability testing are shown. With reference to FIG. 4a), top surface of material system prior to testing is shown.

In FIG. 4 b), top surface of material system post flex testing is shown.In FIG. 4 c), top surface of material system post tensile testing isshown. In FIG. 4 d), a cross section of material system at rupture pointpost tensile testing is shown.

In general, material systems can provide MVTR values similar to those ofstandard commercial textiles, such as PTFE (MVTR ˜550 g/m2/day).Evaluation of MVTR across several material systems compositions (rangingin molecular weight from 43, 99, and 119) revealed a range of accessiblevapor transport (˜500-800 g/m2/day) and demonstrated the tunableproperties of the material systems as a function of polymer molar mass,casting conditions and material system pore size. Elastic moduli (E ˜400MPa) and ductility (λ max ˜0.5) were found to be comparable tocommercial materials, such as GoreTex™, and approximately independent ofstrain rate. Permeability response of the supported material systems canbe practically unaffected by repeated (10×) flex deformation to filmcurvatures of 3 cm⁻¹. The scalability of the material system can bedemonstrated through the fabrication of mid-gauge material systemswatches. These samples can be produce, in a single continuous castingprocess, measuring approximately 4″×5″ and displaying virtually the samehomogeneity, consistent pore structure, and permeability responseobserved at smaller scales.

Referring to FIG. 5, a series of material system configurations arepresented from left to right depicting exposure of material systems ofthe present disclosure to reactants. In accordance with exampleimplementations, material system 10, supported or unsupported, can beexposed to reactant 50. Example reactants are described herein, and caninclude but are not limited to; materials hazardous to human health,such as organophosphorous neurotoxins.

As described herein, material system 10 can include reagents and uponexposure to one or more of these reagents, a product 52 is formed.Product 52, may, for example be a by-product of the degradation of areactant, such as protons upon the degradation of an organophosphorousneurotoxin when reacted with a phosphotriestrerase reagent. This productcan initiate the porous material to locally swell or collapse,modulating permeability as shown in swollen portion 54. In accordancewith this example, the product can be acidic and the pores of the porousmaterial can swell and close upon decrease in pH. Where the porousmaterial is formed of poly(4-vinylpyridine), chains of thepoly(4-vinylpyridine) may stretch to close the pores, for example.

Autonomously, the material systems of the present disclosure can degradea material hazardous to human health to non-hazardous material and alsoprevent the hazardous material from traversing the material system. AsFIG. 5 depicts, this modulation can occur locally to the areas exposedto the reactant.

These material systems may be considered actively-gated material systemswith molecular recognition that mimics skin-like functionality byintegration of enzymes into mesoporous and pH-responsive asymmetricpolymeric films. Theses bio-mimetic material systems can perform a rapidand spatially selective response to specific threat agents and can beintegrated into robust material systems consistent with clothing, suit,mask, and/or protective textile applications.

Referring to FIG. 6, at least one artistic impression of the materialsystem of the present disclosure being cycled or modulated between openand closed configuration upon exposure to a reactant (agent) is shown.As can be seen, the material may be reset upon changes in environment.

The porous material of the material system can be sensitive toenvironmental changes and the products of the reactants and the reagentscan provide these changes. With reference to FIGS. 7A and 7B, forexample, the sensitivity of 4-vinylpyridine (pKa 5.62) to protonate,mesoporous ISV material permeability (Lp) can be highly pH-sensitive.The material systems featured a rapid and effective transition between“open” and “closed” states upon pH change from Lp=1522 Lm⁻²hr⁻¹bar⁻¹ (atpH=7) to Lp=11 Lm⁻²hr⁻¹bar⁻¹ (at pH=3), perhaps as a result ofelectrostatic repulsive interactions leading to thepoly(4-vinylpyridine) chain stretching in the mesopores.

FIGS. 7A and 7B depict the characterization of native ISV behavior andstructure: 7A; pH dependent behavior of the P4VP block of materialssystem; pores in open (deprotonated) and closed (protonated) statesprovide material system permeability changes 7B; material systempermeability of neat and supported material systems in buffer solutionas a function of pH.

Referring to FIG. 8 a)-e), substrate induced dynamic permeabilityresponse of enzyme functionalized material system data is provided asfollows: 8 a) Cyanine dye structure for the colorimetric and fluorescentdetection of environmental pH <4.5. 8b) Visualization of selectivesubstrate turnover in the presence of active enzyme adsorbed on thesurface of dyed material systems (cast from a 9% polymer solution). Testkey: 1. 15.2 mM paraoxon in a 10% methanol water solution; 2. 1 M NaOHsolution, 3. 1 M HCl solution. 8 c) Visualization of vapor-phase DFPsubstrate hydrolysis on dyed enzyme-containing material systems (castfrom a 9% polymer solution) via fluorescence response. 8 d) Reduction inaqueous permeability of enzyme-functionalized material systems inresponse to enzyme substrate, 3.62 μM paraoxon. 8 e) Material systempermeability response was directly related to the magnitude of thechemical challenge.

Visual detection of bound enzyme activity can be demonstrated throughthe use of a pH-sensing cyanine indicator dye (1) (FIG. 8 a). Thestructure of dye 1 was chosen for the pKa=4.7, which is close to that ofthe conjugate acid of P4VP that drives the porous material permeabilitytransition. Upon acidification, the absorption peak of dye 1 shifts fromred (A abs=755 nm, pH >5) to blue (A abs=513 nm, pH <5) and fluorescenceemission is increased in the near-IR region (λ em=773 nm). Thesespectroscopic changes in the dye were used to confirm enzyme functionunder various conditions and predict potential modulation in the ISVmaterial permeability.

With reference to FIG. 8 b), functionalized-material systems weretreated with organophosphate substrates, acid and base. Acids quicklyturned both native and enzyme-treated material system blue. Aqueous basedid not alter material color. Paraoxon (pKa >5), a PTE substrate,produced an indicative “positive” blue response in only those samplespre-treated with enzyme. Samples without enzyme remained unchanged.Enzyme response was also confirmed for vapor-phase agents using thevolatile simulant diisopropylfluorophosphate (DFP). Materialspre-functionalized with enzyme produced a fluorescent response to DFPvapor while material systems without enzyme remained unchanged (FIG. 8c). In addition to positive enzyme function, observation of the drymaterial systems allowed for visualization of response location. Colorchange of the indicator exclusively in the agent-treated area validatedthe high spatial selectivity to the immediate zone of contamination, anaspect of the desired material function.

Transduction of enzyme-mediated substrate hydrolysis into a permeabilityresponse can be evaluated by measurement of the pressure-driven waterflux across material systems in aqueous solution at varying simulantconcentration. Within one minute a reduction of liquid permeability toabout 1 dB of the original value can be observed, demonstrating therapid self-regulating characteristics of enzyme-actuated materialsystems (FIG. 8 d). The rate and magnitude of response increased incorrelation with stimulant challenge (FIG. 8 e). Final material systemflux can be equivalent to the simulated “closed” system (<pH 4.5). Thepermeability transition can be considered stable and highly reproduciblewith negligible loss of enzyme activity or reduction in the level ofmaterial responsivity through several cycles of material system reset(wash solution p>5) and repeat agent exposure.

In accordance with example implementations, materials system 10 can beprepared by operatively associating immobilized reagents with adynamically permeable porous material. These methods can include firstpreparing the dynamically permeable porous material and then operativelyassociating reagents with the porous material. These methods alsoinclude integrating the reagents with the porous material, and thesemethods also can include providing another material, such as a layerupon the porous material with the layer including immobilized reagents.For example, this layer may be considered a reagent support material andthis reagent support material may be operatively associated with theporous material. In the above example implementations, at least aportion of the reagents may be immobilized when associated with theporous material.

In accordance with at least one example implementation, non-solventinduced phase separation can be used to form the dynamically permeableporous material from triblock terpolymers. Porous materials can beprepared using SNIPS (self-assembly with non-solvent induced phaseseparation) of five ISV terpolymers (triblock terpolymers such aspoly(isoprene-b-styrene-b-4-vinylpyridine) with molar masses in therange of 40-120 kg/mol (ISV₄₃, ISV₉₉, ISV₁₁₇, ISV₁₁₈ and ISV₁₁₉). Theporous material exhibited a hierarchical structure that can include athin top surface separation layer of vertically aligned uniformmesopores and a substructure of graded meso- to macropores, with allsurfaces lined by the poly-4-vinylpyridine (V) block of the terpolymer.

Two types of substructures with either a densely packed “sponge-like” orlargely open “finger-like” morphology can be observed depending onfabrication conditions. Variation in polymer composition and porousmaterial casting conditions can be used to control pore size, shape,density and substructure architecture to match the permeability profileof the resulting porous material to respective specifications.

Preparation of the triblock terpolymer ISV and mesoporous asymmetricmembranes derived from ISV can be performed in accordance with TuningStructure and Properties of Graded Triblock Terpolymer-Based Mesoporousand Hybrid Films, Nano Lett, 2011, 11 2892-2900 and/or Understanding theStructure and Performance of Self-Assembled Triblock TerpolymerMembranes, J. Membrane Sci. 2013, 444, 461-468 the entirety of each ofwhich is incorporated by reference herein.

In accordance with example implementations, multiple ISV triblockterpolymers can be synthesized by anionic polymerization. Total numberaverage molar mass, M_(n), weight fraction, f, and polydispersity index,PDI, for these terpolymers as experimentally determined by gelpermeation chromatography (GPC) and proton nuclear magnetic resonance(¹H NMR) are summarized in Table 1 below.

TABLE 1 ISV terpolymer characteristics. M_(n) Sample [kg mol⁻¹] f_(PI)f_(PS) f_(P4VP) PDI ISV43 43 0.24 0.56 0.20 1.02 ISV99 99 0.23 0.63 0.141.20 ISV117 117 0.26 0.60 0.14 1.13 ISV118 118 0.21 0.67 0.12 1.12ISV119 119 0.19 0.65 0.16 1.17

The porous materials can be fabricated by employing a combination ofself-assembly and non-solvent induced phase separation, now referred toas SNIPS. An ISV polymer casting solution can be prepared by dissolvingISV polymer into a co-solvent mixture comprised of a 7:3 ratio (byweight) of 1,4-Dioxane (DOX) and tetrahydrofuran (THF). The solution canbe pipetted onto a glass substrate for neat, unsupported material.Supported material can be cast directly onto porous nylon substrates,purchased from Sterlitech Inc., taped to glass substrates. The polymersolution can be cast by a doctor blade with a gate height of 220 μm andallowed to evaporate for a specified amount of time before the films areimmersed into a deionized water bath. Unless mentioned otherwise,materials can be cast from a 16% (ISV₄₃), 12% (ISV₉₉ and ISV₁₁₈) or 11%(ISV₁₁₇ and ISV₁₁₉) (by weight) polymer solution. These materials can becast on top of a 0.2 μm (ISV₁₁₇), 0.1 μm (ISV₄₃, ISV₉₉, ISV₁₁₉) or 0.04μm (ISV₁₁₈) nylon support.

Referring to FIG. 9a )-f), SEM images are provided of preparedmaterials; 9 a), image of ISV₁₁₉ material cast on nylon; 9 b) & c), SEMmicrographs of the top surface of ISV₁₁₉ material; 9 d) & e), SEMmicrographs of the cross section of the ISV₁₁₉ material; 9 f), TEMmicrograph of ISV₁₁₈ material separation layer stained with PTA.

Referring to FIGS. 10A and 10B as well as 11 a) and 11 b), materialscast from ISV₁₁₇ and ISV₁₁₈ can exhibit an open “finger-like”substructure while materials cast from ISV₄₃, ISV₉₉ and ISV₁₁₉ canprovide a dense “sponge-like” substructure. FIG. 10A depicts SEMmicrographs of neat cross sections of ISV₁₁₇ material with “finger-like”substructure (left) and ISV₁₁₉ material with “sponge-like” substructure(right). FIG. 10B depicts the permeability of neat ISV₁₁₇ and ISV₁₁₉materials in buffer solution as a function of pH. Referring to FIG. 11:a) depicts SEM micrographs of the surface morphology and neat crosssection of ISV₁₁₈ material with “finger-like” substructure and b)depicts permeability in buffer solution as a function of pH forsupported ISV₁₁₈ material cast on 0.04 μm nylon supports.

Additional values for the absolute permeabilities in the “open” and“closed” state of neat and supported ISV₁₁₇ and ISV₁₁₉ materials areindicated in Table 2 below.

TABLE 2 Absolute permeabilities in the “open” and “closed” state of neatand supported ISV₁₁₇ and ISV₁₁₉ materials. “open” state (pH = 7)“closed” state (pH = 3) (Lm⁻²hr⁻¹bar⁻¹) (Lm⁻²hr⁻¹bar⁻¹) Neat ISV117 152232 Supported ISV117 504 27 Neat ISV119 747 29 Supported ISV119 257 11

Referring to FIG. 12, a) depicts SEM micrographs of ISV₁₁₇ materialscast from 11% (left) and 9% (right) polymer solution with “finger-like”cross sections of neat ISV₁₁₇ materials (bottom). The top images showsurface morphology of nylon-supported ISV₁₁₇ materials. b) depictspermeability of supported ISV_(117,) casted from 11% and 9% polymersolution, materials in buffer solution as a function of pH. Withparticular reference to FIG. 12, a) materials cast from ISV₁₁₇ at 11%(left) and 9% (right) polymer solution have similar surface morphologiesand “finger-like” substructures. These materials perform similarly (i.e.permeability as a function of pH) but differ in absolute permeabilityvalues due to polymer concentration. It is assumed here that materialscast from solutions that vary slightly in polymer concentration havesimilar properties and performance values.

Additional values for the absolute permeabilities in the “open” and“closed” state of neat and supported ISV₁₁₈ materials are provided inTable 3 below.

TABLE 3 Absolute permeabilities in the “open” and “closed” state of neatand supported ISV₁₁₈ materials. “open” state (pH = 7) “closed” state (pH= 3) (Lm⁻²hr⁻¹bar⁻¹) (Lm⁻²hr⁻¹bar⁻¹) Neat ISV118 1082 10 SupportedISV118 491 15

Preparation of the material system can also include adsorbing thereagents to the porous material. This can include covalently bonding thereagents to the porous material as well as integrating the reagent intothe porous material. Accordingly, the reagents can be immobilized on tothe surface of the material using methods including but not limited toadsorption, bio-affinity or covalent conjugation. As described, thereagent can include more than one co-immobilized reagent including butnot limited to enzymes, metal organic frameworks (MOFs), metal oxides,nucleophilic amines and oximes.

Adsorption can be used as a reagent (enzyme) immobilization method toattach a broad array of protein structures to polymer surfaces. Enzymecoupling can be accomplished by immersion of porous materials intoconcentrated enzyme solutions, harnessing the strong interactionsbetween enzymes and P₄VP on the outer surface of the ISV material.Coupling can also be accomplished by dropcasting, printing or othersimilar deposition methods.

To impart target-specific response characteristics, supported ISVmaterials can be conjugated to hydrolase enzymes, which havedemonstrated use in the identification, quantitation, anddecontamination of threat agents. In specific embodiments, due to thepH-based material response mechanism, functionalization of the ISVmaterial may focus primarily on enzymes that act on relevant substratesto produce highly acidic products.

In accordance with example implementations, porous materials can beincubated in solutions of PTE enzyme (1-20 mg mL⁻¹, 10 mM CAPSO, pH 9.4,500 μL per 100 mm² material system surface area) for 16 hours at 4° C.on an orbital shaker at low speed. For samples containing dye 1, 100 μLof a 10 mg mL⁻¹ stock solution in water can be added to the proteinsolution for every 100 mm² material system surface area.Post-immobilization, samples can be washed (3×) with 10 mM CAPSO, pH 9.4buffer for 30 minutes at 4° C. on an orbital shaker at low speed priorto testing.

Direct phosphotriesterase hydrolysis assays can be performed on aMolecular Devices SpectraMax M2 ^(e) spectrophotometer in 96 well platesfor solution-phase enzyme samples (100 μL reaction volume, 0.35 mm pathlength, 5 min kinetic duration) and on a Beckman Coulter DU530 UV/VISspectrophotometer, transferring aliquots of assay solution samples to acuvette for solid-phase enzyme samples (1 mL volume, 1 cm path length,10 min kinetic duration). All assays can be completed at 25° C. againstethyl paraoxon and the rates measured by monitoring the release ofp-nitrophenol (ε405=17100 M⁻¹cm⁻¹). Substrate stock solutions can beprepared by the dissolution of diethyl paraoxon in dry methanol (152 mM)followed by dilution of the methanol stock in deionized water (15.2 mM).For the enzymatic reaction, aliquots of the 15.2 mM paraoxon stock canbe added to a mixture of enzyme in reaction buffer (50 mM CAPSO, 50 μMCoCl₂, pH 9.0) to give a final concentration of 1.52 mM. A dilutionseries of enzyme concentrations can be used for solution-phase samples(final enzyme concentrations range from 1 ng-10 μg mL⁻¹) to achieve alinear rate. For solid-phase samples, a section of material can besubmerged in an adequate volume as to maintain a linear rate over thecourse of the kinetic assay (typical conditions: 3 mm diameter circle, 2mg mL⁻¹ enzyme incubation, 12 mL assay buffer). The initial enzymaticrates can be corrected for the background rate of spontaneous paraoxonhydrolysis in the absence of enzyme. Specific activity values of thesolution-phase samples can be calculated using the following formula:

Specific Activity (umol min⁻¹.mg⁻¹)=ΔmAUmin⁻¹×(1×10⁶)×DF×(1000×17100×0.35×C)⁻¹, where ΔmAU min⁻¹=ΔmAU min⁻¹test−ΔmAU min⁻¹ blank, DF is the dilution factor, 17,100 M⁻¹ cm⁻¹ is themolar extinction coefficient of p-nitrophenol, C (in mg L⁻¹) is theprotein concentration of enzyme stock solution and 0.35 cm is the pathlength of light.

Quantitation of active enzyme loading of solid-phase samples can becalculated using a calibration curve prepared from the rates ofenzymatic paraoxon hydrolysis (linear regression of absorbance vs. time)for a series of solution-phase enzyme standards of known concentrationand identical specific activity as that incubated with the materialsystem. The resulting equation can then be compared against thehydrolysis rates obtained for the solid-phase samples to calculateenzyme mass loading (ng) per unit area (mm²).

Referring to FIG. 13, images of protein adsorbed to homopolymer samplesspun-cast on silicon wafers are provided. Thickness measurements ofenzyme coatings adsorbed on P₄VP reference films using ellipsometry(Table 3 (above)) revealed the formation of enzyme monolayers that werestable against desorption during repeated washing with deionized water,detergents, and ionic solutions with pH ranging between 4-10.

The ellipsometry measurements can be conducted using a BeagleholeInstruments Picometer phase-modulated ellipsometer equipped with ahelium-neon laser (λ=632.8 nm). The angle of incidence was varied from70-80°, and analysis was completed using TF Companion software (Version3.0, Semicon Software, Inc.) and a four layer, homogeneous film model(semi-infinite silicon+silicon dioxide+polymer+adsorbedenzyme+semi-infinite air). Thin film material systems of PI, PS, P₄VP,and ISV with thicknesses between 10-20 nm can be spin cast from 0.1 wt.% solutions in toluene (PI, PS, and ISV) and a 1:1 mixture of acetoneand ethanol (P₄VP) onto silicon wafers. The polymer-coated wafers canincubated in a solution of PTE enzyme (9.7 mg mL⁻¹, 10 mM CAPSO, pH 9.4)for 16 hours at 4° C. on an orbital shaker at low speed. The layerthickness can be successively determined for the silicon dioxide layer(2-3.5 nm), the material layer (10-20 nm), and the adsorbed enzyme.Literature values of refractive indices for PI (1.51), PS (1.59), P₄VP(1.581), ISV (1.5707), and dry enzyme (1.53) were used for the analysis.

TABLE 4 Thickness values of silica layer on silicon support, homopolymerlayer, and protein adsorption layer as derived from analysis ofellipsometry measurements. Protein Material Silica (Å) Polymer (Å) (Å)Protein (ng mm⁻²) Polyisoprene 34.8 ± 0.4  98.9 ± 8.9  3.0 ± 2.3 0.39 ±0.29 Polystyrene 26.2 ± 2.2 153.6 ± 8.2 24.0 ± 8.2 3.12 ± 1.06 Poly-4-20.0 ± 0.3 200.5 ± 5.2 35.8 ± 5.2 4.65 ± 0.67 vinylpyridine ISV 21.1 ±0.3 142.5 ± 2.2 23.6 ± 5.4 3.06 0.07

Referring next to FIG. 14, representative quantities of PTE(YT) enzymeadsorption per unit surface area (ng mm⁻²) to supported ISV₁₁₉ accordingto solution-phase enzyme incubation concentration data is depicted.Referring to FIGS. 15A and 15B, data depicting stability ofISV₁₁₉-adsorbed PTE(YT) enzyme activity to dry storage conditions in theabsence (a) or presence (b) of excipient is shown.

As shown, the material system retained activity in solution and upondrying, even after extended storage (FIGS. 14 and 15A-B). Enzymestability during dry storage on supported ISV₁₁₉ materials can beassessed in the presence and absence of stabilizing excipient for arange of temperatures over a 30 day incubation period. Enzymefunctionalized material systems can be prepared as described herein.Upon completion of the final rinse, excipient stabilized materials canbe subjected to an additional incubation in a 1% collagen hydrolysatesolution (3 mm diameter ISV₁₁₉, 500 uL solution, 30 min, 4° C.), afterwhich both native and stabilized materials can be lyophilized to drynessand individually packaged under nitrogen in Mylar bags for storage.

Samples can be incubated at 4, 25, 40, or 60° C. for up to 30 days, withactivity time points collected on days 0, 10, and 30. At each time pointthe enzyme activity can be assessed by >4 replicates. Pretreatment ofsamples with excipient significantly helped to maintain enzyme activityof the dried samples as measured on day 0.

As indicated, material system 10 can also include a support structuresuch as a nylon-based support structure. This support structure can beincluded before or after the association of the immobilized reagents.

Phosphotriesterase (PTE) can be obtained from Novozymes (Davis, CA) andexchanged into 50 mM potassium phosphate, 100 uM cobalt chloride, pH 8.0for storage at 4° C. until use. Enzyme variants PTE(RN-YT) and PTE(C23)can be prepared in-house according to known procedures. pH-sensitive dye1 can be custom synthesized and purchased from American Dye Source, Inc.(Quebec, Canada). Ethyl paraoxon (Chem Service, Inc., >98%),Diisopropylfluorophosphate (Sigma-Aldrich, >97%)

An evaporative dish method, based on the British Standard BS 7209, wasused to determine the MVTR in material system samples. The Turl dishassembly consists of a dish, triangular support, and cover ring. Thetest specimen is comprised of two circular material system samples, witha total area of 402 mm², anchored to a circular transparency film,purchased from C-Line Products, Inc. (No. 60837), using epoxy. The testspecimen was sealed over the mouth of the dish containing deionizedwater and the triangular support to maintain a ˜10 mm air gap. The coverring was placed above the test specimen and adhesive tape was appliedaround the circumference of the competed assembly. The assembly waspositioned into a turntable and the experiment was conducted in acontrolled atmosphere of 20° C. and 65% relative humidity. Theassemblies were weighed on a balance with a resolution of 0.01 g. Eachassembly was weighed daily up to five days in order to assure fullequilibration. Data for calculation of MVTR values were taken on dayfive.

The MVTR(g m⁻² day⁻¹) was calculated as: MVTR=24M(At)⁻¹, where M is theloss in mass of water in grams, t is the time period in hours, and A isthe area of the material system sample in m².

In addition to the three nylon-supported ISV materials (ISV₄₃, ISV₉₉,and ISV₁₉₉), dishes were evaluated in the open and closed states forreference. Values obtained from these measurements were used asbenchmarks in addition to literature values reported for relevantcommercially available material (i.e. PTFE and PU, see FIG. 3b ).

Intrinsic water vapor resistance was calculated as:Ret=R_(f)(RT)(M_(w)ΔH_(vap))⁻¹, where R_(f) is the intrinsic masstransfer resistance of the sample, R is the universal gas constant, T istemperature, M_(w) is molar mass of water, and ΔH_(vap) is the enthalpyof vaporization of water.

TABLE 5 ISV terpolymer resistance to evaporative heat transfer. SampleR_(et) [m²-Pa Watt⁻¹] tefzel film 2690 ISV119 “open” 8.8 ISV119 “closed”9.6 Supported ISV119 “open” 13.2 Supported ISV119 “closed” 14.2 opencell 6.2

Tensile testing of the materials can be performed on an Instron (model4442) equipped with a 1 kN load cell with loading strain rates of 1, 10,and 100 mm min⁻¹. The samples were 13 mm×20 mm with a thickness of 0.11mm. Stress-strain curves were constructed, and the Young's Modulus wasdetermined by calculating the slope within the proportionality limit ofthe curve. The toughness can be calculated by integrating thestress-strain curve over the entire deformation range. Samples can befixed and repeatedly flexed (three sets of 10 flexes) to a curvature of3 cm⁻¹ at a rate of 0.5 Hz.

The entirety of both “Biocatalytic Stimuli-Responsive AsymmetricTriblock Terpolymer Membranes for Localized Permeability Gating” byPoole et al, Macromolecular Rapid Communications, 2017, 1700364, andSupporting Information for Macromol. Rapid Commun., DOI:10.1002/marc.201700364 “Biocatalytic Stimuli-Responsive AsymmetricTriblock Terpolymer Membranes for Localized Permeability Gating” byPoole et al, are both incorporated herein by reference.

Enzymes can be incorporated into ISV membranes to test their ability tohydrolyze simulants on the surface of the membrane in low (<20%) andhigh (>90%) humidity. For example, 8 mm ISV membranes can be coated withphosphotriesterase (PTE), haloalkane dehalogenase(DHG), or both andallowed to dry. In accordance with one example, enzyme can be providedat 51.7 μg/mm², 25.9 μg/mm², and 5.2 μg/mm². The enzyme coated membranesand a breakthrough membrane can be incorporated into the cap of a GCvial containing artificial sweat. This vial can then be placed into a 20mL vial containing another GC vial with either water (>90% humidity) orsaturated lithium chloride (<20% humidity). The larger vial may becapped, and the internal environment allowed to equilibrate for 15minutes. 500 μg of Diethyl VX per mm² can then be added the membrane andallowed to incubate overnight. The membranes may then be extracted forGC-MS analysis.

In accordance with another example, ten different levels of enzyme wereloaded within the membranes ranging from 50-2.5 μg/mm² (See Table 6Below) These membranes were then tested for surface decontamination ofthe simulant diethyl VX at a load of 500 ug/cm² under high (>90%) or low(<20%) humidity conditions. After a 24 incubation the membrane andbreakthrough material were both extracted per the above protocol toquantitate decontamination and agent breakthrough within the sample. Thegraphs of FIG. 16 show with the green dotted line the loading of enzymerequired to achieve full decontamination of the simulant under eachcondition.

TABLE 6 Enzyme Membrane Load at >90% and <20% humidity. 50 ug/mm² 25ug/mm² 5 ug/mm² 2.5 ug/mm² 500 ng/mm² 250 ng/mm² 50 ng/mm² 25 ng/mm² 5ng/mm² 2.5 ng/mm²

Using the same format as described above, the study can be expanded toinclude contamination of simulants diisopropylfluorophosphate (DFP),ethyl paraoxon, and dibromoethane (DBE), in addition to DEVX. Eachsimulant can be tested under both high and low humidity environment.Under the loading conditions of 51 μg/mm² for PTE and 20 μg/mm² forHaloalkane Dehalogenase (DHG), membranes were separately challenged with500 μg/cm² of Diisopropyl fluorophosphate (DFP), Paraoxon orDibromoethane (DBE) under dry (<20% humidity) and humid (>90% humidity)conditions. GC-MS analysis demonstrated that full hydrolysis of eachsimulant occurs under humid conditions. The data presented in FIG. 17shows that even though 500 μg/cm² of DBE and DFP were added, some of itvolatilized due to the vapor pressure of the simulants. The rest wasremoved by enzymatic hydrolysis. Those with lower vapor pressures,paraoxon and DEVX remained on the control membrane or were hydrolyzed bythe enzyme.

Under humid conditions, 500 μg/cm² DEVX can be added tophosphotriesterase loaded membranes. Samples were analyzed by GC-MSanalysis at 0, 1, 5, 10, 30 and 60 minutes. With 51 μg/cm² enzyme loadedonto an ISV membrane, a hydrolysis of >99% of a 500 μg/cm² challenge canbe observed within the first 30 minutes of the challenge withdecontamination rates for this time ranging from 135 to 0.3 μg/cm²*min,as shown in FIG. 18.

To determine the ability of the enzyme-loaded membranes to respond tosequential DEVX challenges, phosphotriesterase enzyme was loaded ontoISV membranes at 51 μg/mm². Additive challenges of 500 μg/cm² (250 μgper 8 mm membrane) can be performed at 0, 1 and 2 hours (1.5 mg/cm²cumulative challenge). Membranes may be analyzed for the presence ofremaining DEVX at 1, 2 and 3 hours.

The results demonstrate that DEVX hydrolysis continues after the initialchallenge and even after the third challenge of 500 μg/cm², >90% of theDEVX is hydrolyzed with no breakthrough observed as shown in FIG. 19.

Moving toward assessing the ability of the material to address multipletypes of challenges in a single form factor, the best method ofperforming challenges with a mix of agents may be determined. 500 μg/cm²of DEVX and DBE, as well as serial dilutions of each, can be eithermixed or added separately to a chloroform extraction with internalstandard and analyzed by GC-MS and the resulting data shown in FIG. 20.

Methods used to quantitate agent permeation can include the following:

Samples analyzed by this method are shown in FIG. 21 for comparison ofvapor permeation, no membrane (i.e. open system), PTFE, Nitrile, and theISV membrane.

The headspace gas chromatography method outlined by the ECBC may be usedto analyze DFP simulant permeation through ISV membrane and severalcontrol samples. Enzymatic loading can be performed via drop-casting.Horseradish Peroxidase (HRP) {E.C. 1.11.17} was utilized as a controlfor Phosphotriesterase (PTE). HRP has a molecular weight of 44 g/mol ascompared with PTE, which has a molecular weight of 35.90 g/mol.Analyzing the protein electrostatics, the overall protein charges arealso similar with PTE having an overall charge of −2.6 while HRPcontains an overall charge of −2 under neutral conditions.

Upon receiving the membranes, they may be treated for the vial-in-vialprotocol. This entailed as mentioned previously rinsing the membraneswith water, drying the membranes to remove any residual moisture,drop-casting enzyme onto the membrane and then drying the enzyme loadedmembranes. Once dried the membranes can then conditioned for 24-48 hoursin a humid environment at 37° C. Enzyme loading within the material maybe performed at a protein loading concentration of 7 μg/mm². Thisconcentration dried upon the membrane produces a uniform enzyme coatingwhich does not appear to flake or clump. The membranes may than betested in the previously described vial-in-vial experimentation setupwith 500 μg/cm² Diisopropyl flurophosophate (DFP) to monitor vaporpermeation across the enzyme loaded ISV membrane. Triisopropyl Phosphate(TIPP) was utilized as the internal standard reference. The temperatureof analysis was 37° C.

After 45 minutes, the Free Diffusion samples recovered 83% of the 500μg/cm² initial DFP loaded in the challenge vial. The mere addition ofthe pristine ISV₄₃ reduces the vapor permeation by 39.5% for the sametime-course. Examining the enzyme loaded samples after 45 minutes, theHRP alone provided an 82% reduction in free diffusion. This is mostlikely due to steric hinderance and pore blockage since HRP shows littlecatalytic activity toward DFP as previously documented. The PTE loadedmembranes for the same duration record values under the establishedcalibration range. These effects are amplified as seen with the lowersimulant challenge of 5 μg/cm² DFP. In analyzing the vapor permeationafter 45 minutes, free diffusion recovers approximately 64% of initialDFP challenge. See for example, FIG. 22.

An extended time course examination was conducted monitoring vaporpermeation from 1 hour after initial simulant loading up to 24 hours.For this experiment, twice the amount of the standard 500 μg/cm²challenge was utilized 1000 μg/cm² and the data is shown in FIG. 23.Examining free diffusion, the maximum concentration of vapor in theheadspace was achieved at the 1 hour mark, decreasing at each subsequenttime point. Even with these extend dwell times, there was no significantincrease in DFP permeation for the PTE loaded ISV membranes.

To determine the effect of enzyme loading on the MVTR of SNIPSmembranes, pure and blended ISV membranes were loaded with proteinsolution and the change in MVTR was measured. This is an importantfactor as MVTR is directly related to the material's thermal burdenperformance specifications. Replicate membranes of pure ISV (YML644A andYML644B), blended ISV:ISO (9:1A ISV:ISO and 9:1B ISV:ISO), and blendedISV:IS(HEMA) (9:1A IS(HEMA) and 9:1B IS(HEMA)) were tested and the datashown in FIG. 24.

Asymmetric membranes were fabricated by employing a hybrid processcombining block copolymer self-assembly with a non-solvent induced phaseseparation process (SNIPS). Pure ISV membranes were cast from a 11% (byweight) ISV₁₃₈ polymer solution in a solvent mixture of 1,4-dioxane(DOX) and tetrahydrofuran (THF) (7:3 by weight). For the ISV:ISO blend,a ternary solvent mixture of DOX, THF, and acetonitrile (MeCN) was usedas the solvent system. The casting solutions were prepared by separatelydissolving 11% and 18% of ISV and ISO, respectively, in a solvent systemconsisting of DOX/THF/MeCN (˜67/28/5 wt %) at 300 rpm overnight. TheISV:ISO weight ratios of 9:1 was maintained in the individual castingsolutions prior to blending. The individual casting solutions containingthe desirable blend weight ratios were then mixed and stirred togetherat 300 rpm for 10 minutes to form a hybrid casting solution. The dopesolution was cast by doctor blade with a gate height of 220 μm onto a0.1 micron nylon substrate using an automated set-up. After 100 secondsfor pure ISV and 120 seconds for blended ISV:ISO membranes, the thinfilm was immersed into a coagulation bath of de-ionized water. Samplesof ISV:IS(HEMA) membranes in a 9:1 weight ratio were prepared andsupplied by Terapore.

An evaporative dish method, based on the British Standard BS 720921, wasused to determine the MVTR in membrane samples. The Turl dish assemblyconsists of a dish, triangular support, and cover ring. The testspecimen is comprised of two circular membrane samples, with a totalarea of 402 mm₂, anchored to a circular transparency film, purchasedfrom C-Line Products, Inc. (No. 60837), using epoxy. The test specimenwas sealed over the mouth of the dish containing deionized water and thetriangular support to maintain a ˜10 mm air gap. The cover ring wasplaced above the test specimen and adhesive tape was applied around thecircumference of the completed assembly. The assemblies were positionedinto a turntable and the experiment was conducted in a controlledatmosphere at 20° C. and 65% relative humidity. The assemblies wereweighed on a balance with a resolution of 0.01 g. Each assembly wasweighed daily up to six days in order to assure full equilibration.After six days, the pristine membranes were loaded with 60 microlitersof protein solution (bovine serum albumin; BSA in 0.1 M PBS) with aconcentration of 130 g/L. Each assembly was weighed daily. The reportedMVTR values were averaged over five days. The MVTR (g/m₂/day) wascalculated as: MVTR=24M/At, where M is the loss in mass of water ingrams, t is the time period in hours, and A is the area of the membranesample in m₂.

The MVTR values of the SNIPS membranes are not significantly affected bythe loading of protein at such a high concentration. This result isencouraging as this indicates that enzyme may be loaded within themembrane at high concentrations without significantly impeding themoisture vapor flow through the membrane in the open state. It isimportant to note that the variability in the MVTR of the open referencecan be due to the slight variability in ambient temperature and humidityof the room in the summer months.

1. An autonomous localized permeability material system comprising: adynamically permeable porous material; and immobilized reagentsoperatively associated with the porous material in sufficient proximityto trigger a localized change in material pore size upon reagentreaction.
 2. The material system of claim 1 wherein the porous materialcomprises a polymer.
 3. The material system of claim 1 wherein theporous material is nano to macroporous.
 4. The material system of claim1 wherein the porous material has an elastic moduli of greater than 300MPa.
 5. The material system of claim 1 wherein the immobilized reagentis stoichiometric or catalytic.
 6. The material system of claim 1wherein the immobilized reagent comprises one or more of enzymes, metalorganic frameworks, metal oxides, and oximes.
 7. The material system ofclaim 1 wherein the immobilized reagent is integrated with thedynamically permeable porous material.
 8. An autonomous localizedpermeability material system preparation method comprising operativelyassociating immobilized reagents with a dynamically permeable porousmaterial.
 9. The method of claim 8 further comprising using non-solventinduced phase separation to form the dynamically permeable porousmaterial.
 10. The method of claim 9 wherein the permeable porousmaterial comprises polymers.
 11. The method of claim 8 furthercomprising adsorbing the reagents to the dynamically permeable membrane.12. The method of claim 8 further comprising covalently bonding thereagents to the dynamically permeable membrane.
 13. The method of claim8 further comprising integrating the reagent into the dynamicallypermeable membrane.
 14. The method of claim 8 further comprisingproviding a reagent support material and associating the supportmaterial with the dynamically permeable membrane.
 15. A method forautonomously modifying localized permeability of material, the methodcomprising: providing a dynamically permeable porous materialoperatively associated with immobilized reagents; reacting the reagentswith a reactant to form a product; and exposing the product to thedynamically permeable porous material, the exposing of the productmodulating the permeability of the material.
 16. The method of claim 15wherein the reactant is hazardous to human health, and upon reaction isrendered non-hazardous.
 17. The method of claim 15 wherein the reagentis a phosphotriesterase and the reactant is an organophosphorousneurotoxin,
 18. The method of claim 15 wherein the product is acidic andpores of the porous material close upon decrease in pH.
 19. The methodof claim 18 wherein the material comprises poly(4-vinylpyridine) andchains of the poly(4-vinylpyridine) stretch to close the pores.
 20. Themethod of claim 15 wherein the porous material has an elastic moduli ofgreater than 300 MPa.